NEMA 48 frame split-phase general purpose AC motors have a standard 1/2' diameter, 1-1/2' length shaft whose center is 3' above the base mounting surface. Variations to the frame's standard dimensions and design are indicated by a letter designation following the frame number, such as 48Z or 48Y. The letter “Z” indicates that the frame has a nonstandard shaft, and “Y” indicates a nonstandard mounting. These frame standards and letter designations are defined by the National Electrical Manufacturers Association (NEMA).